Tinnitus is the perception of sound in the human ear in the absence of corresponding external sound(s). Tinnitus is considered a phantom sound, which arises in the auditory system. For example, a ringing, buzzing, whistling, or roaring sound may be perceived as tinnitus. Tinnitus can be continuous or intermittent, and in either case can be very disturbing, and can significantly decrease the quality of life for one who has such an affliction.
Tinnitus can, to date, not be surgically corrected and since, to date, there are no approved effective drug treatments, so-called tinnitus maskers have become known. These are small, battery-driven devices which are worn like a hearing aid behind or in the ear and which, by means of artificial sounds which are emitted, for example, via a hearing aid speaker into the auditory canal, to thereby psycho acoustically mask the tinnitus and thus reduce the tinnitus perception.
Although present day tinnitus maskers to a certain extent may provide immediate relief of tinnitus, the masking sound produced by them is very monotonous and therefore unpleasant for the user of such a masker. Investigations show that tinnitus is a condition that requires long term treatment in order to achieve good results. However, the listening to highly monotonic sounds signals as masking sounds during such a long time may be a severe annoyance to a user of such a masker.
An example of a present day tinnitus masker is disclosed in EP 2 132 957 where a noise signal is random or pseudo randomly modulated.
Another example is disclosed in US 2009/0028352 where a recorded natural sound is combined with a computer generated sound. The computer generated sound emulates the recorded sound. The combined sound has greater ratios between minimum and maximum amplitude envelopes compared to the recorded natural signal.